Elucidation of stability profiles of common chemistry analytes in serum stored at six graded temperatures

Abstract

Background Many reports address the stability of biochemical analytes in serum. However, studies covering a wide range of storage temperatures are unavailable. Using equipment enabling precise temperature control, we investigated the effect of six different storage temperatures on serum analytes. Methods Serum specimens from seven healthy volunteers were obtained and divided into multiple aliquots for storage at −30, −20, −10, 0, 4, and 25 °C. On days 1, 3, 7, 14, 28 and 56, the aliquots stored at each temperature were relocated to a deep freezer maintained at −80 °C. On day 60, all aliquots were measured collectively for 13 major chemistry analytes. Results (1) At 25 °C, alanine aminotransferase (ALT), creatine kinase (CK), aspartate aminotransferase (AST) and total bilirubin (TBil) were very unstable especially on day 7 and later. (2) At ≤4 °C, alkaline phosphatase (ALP), γ-glutamyltransferase (GGT), amylase (AMY), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), triglyceride (TG), TBil and complement component-4 (C4) were generally stable and were very stable at 25 °C until day 14. (3) Between −20 and 4 °C, especially at −10 °C, test results of ALT, AST and lactate dehydrogenase (LDH) showed prominent decreases, but their stability was greatly improved at −30 °C. (4) In contrast, the value of complement component-3 (C3) increased at ≥− 20 °C. (5) At −30 °C, test results of all analytes were generally very stable except for ALT and CK, which showed noticeable reductions in activity after 14 days. Conclusions This is the first study to assess the stability of serum analytes at six graded temperatures simultaneously. Each analyte has a unique stability pattern for a range of temperatures.

Test results comparison and sample stability study

“…Demeester et al reported similar results after a 7-day storage period in BD Barricor plasma tubes for albumin, ALP, AST, glucose, LD, Na and K ( 17 ). Shimizu et al obtained results comparable to ours for AST and LDH in serum samples after storing samples for 7 days on 4 °C ( 20 ).…”

Stability of lactate dehydrogenase in plasma at different temperatures: post-analytical storage

“…The results of our study are consistent with the ones obtained by Shimizu Y, An B and Heins M [3][4][5], who reported that activity decreases in refrigerated samples, whereas it remains stable at RT. In contrast, Oddoze C [6] observed an increased activity.…”

Estabilidad de la alanina aminotransferasa en suero. Efecto del modelo de estudio, la concentración catalítica inicial y la plataforma analítica

“…De acuerdo con nuestros resultados, se observa una influencia muy importante de la temperatura en la estabilidad, siendo ésta cinco veces inferior a temperatura ambiente que en muestras refrigeradas. La mayor pérdida de estabilidad a temperatura ambiente concuerda con lo observado de manera general [22,23] Hasta donde sabemos, este es el primer estudio que evalúa la influencia de variables no habituales en la estabilidad de la ALT, como son la concentración catalítica inicial, la plataforma analítica y el modelo experimental [7,9,11].…”

“…Lo contrario pasaría con los individuos con concentración catalítica de ALT muy estable en el tiempo, para los cuales se podrían conservar las muestras durante periodos superiores. Este efecto podría en parte deberse a la presencia de isoenzimas termosensibles, como se sugiere por ejemplo para la lactato deshidrogenasa [23].…”